"I'm not speaking because I feel I should be heralded," Lane told "20/20's" Elizabeth Vargas in an exclusive interview. "I'm just speaking because they're completely lying about the amount of dancing that Natalie did in the movie."

In "Black Swan," Portman played a talented and tormented ballerina, whose searing descent into madness is mirrored by her incredible dancing on stage. But a recent controversy sprang up after Lane claimed to not only have danced in some of the movie's most unforgettable scenes that earned Portman a best actress Oscar, and that filmmakers asked her to refrain from talking about her role.

After she was interviewed by Glamour magazine for an article titled "The Real Black Swan," Lane, a soloist for the prestigious American Ballet Theatre, said one of the film's producers called and told her to keep quiet about the extent of her performance.

"He asked if I would please not do any more interviews until after the Oscars because it was bad for Natalie's image," Lane said. "They were trying to create this image, this facade, really, that Natalie had done something extraordinary. Something that is pretty much impossible ... to become a professional ballerina in a year and half. Even with as hard as she worked, it takes so much more. It takes twenty-two years, it takes thirty years to become a ballerina."

Jess Cagle, the managing editor for Entertainment Weekly, agreed, saying, "they diminished what Sarah did by telling Sarah to shut up and not talk and don't let anyone know."

Portman's face was superimposed onto Lane's body through special effects called "face replacement" in pivotal dance scenes to make it appear as if it were Portman executing technically sophisticated moves.

In a written statement, "Black Swan" director Darren Aronofsky said, "Here is the reality. I had my editor count shots. There are 139 dance shots in the film -- 111 are Natalie Portman untouched. Twenty-eight are her dance double Sarah Lane. If you do the math, that's 80 percent Natalie Portman."

"It's possible if you're counting the close-ups of her face as actual dancing shots. I don't call close-ups of her face actual dancing," Lane said.

"Black Swan" editor Andy Weisblum agreed to take a closer look for "20/20." "There are about 35 shots that are full body shots in the movie. Of those 35 shots, 12 are Natalie, and then the rest are Sarah," Weisblum said. "But over the overall film, Natalie did a lot more than that. I mean, she did most of the other shots. It was sometimes hard for me to tell the difference as the editor, it was so close."

Sarah Lane's Contract: No Onscreen Credit for 'Black Swan'

But Lane only has praise for Portman's acting triumph. "I think she is a really beautiful actress," the ballerina said. "I loved working with her. And she was really focused on her character every day. I definitely think she deserves, all the credit that she got with the Oscar."

Lane acknowledged that she'd signed a contract that would not guarantee her on-screen credits.

"I didn't really specify anything in my contract about getting onscreen credit or anything," said Lane. "I didn't do the movie to get fame or recognition or anything."

Lane said her feelings about being credited changed late last year after Portman received an Oscar nomination for best actress and the movie's backers began an aggressive campaign on the actress's behalf.

"There's so much emotionally that goes into motivating yourself and being able to physically push yourself to reach a certain level, that you have to reach to be a professional ballerina with one of the biggest ballet companies in the world and to sustain that standard over a whole career," Lane said. "It really hurts for someone to say that, they got a personal trainer and they became what I spent blood, sweat and tears doing every day, all my life, in just a year and a half."

"A lot of the campaign was focused on the physical preparation, the transformation," Cagle said. "The Academy loves it when an actor does something besides act in a movie. There was in a lot of the marketing materials for "Black Swan," certainly the implication that Natalie became a great world class ballet dancer."

Lane acknowledged that while Portman trained hard for the film, her dancing technique was nowhere near as good as hers.

"I've been doing this for 22 years, and to say that someone trained for a year and a half and did what I did is degrading not only to me but to the entire ballet world," Lane said.

Wendy Perron, editor-in-chief of Dance Magazine, a choreographer and a dancer, said she knew of Lane's role in "Black Swan" and wondered why a soloist ballerina whose technical skills were vital to the complicated dance sequences was being cast out of the limelight.

"She's an artist," Perron said. "It's not just that it was difficult. It's that she brought an artistry to it, and Natalie Portman is a dramatic artist, a film artist. But Sarah Lane is a dance artist, and she helped make the movie what it was. ... It bothered me. I think she should get credit for it."

Perron wrote her opinion in a blog that was soon picked up in the national media, and "Black Swan" filmmakers moved swiftly to defend their star.

Portman has continued to decline to comment on the controversy, and told E! News last week, "I had a chance to make something beautiful with this film, and I don't want to give in to the gossip."

For Lane, the silver lining in this controversy may just be that ballet is taking center stage in a national discussion. An unanticipated opportunity to share the commitment and dedication of all ballet dancers.

"I have so much respect for this art form and the people who are able to do it so beautifully and I want to stand up for that," she said. "I want people to know how hard we work as professional dancers. What is not necessarily, really portrayed in the movie, is the beauty that ballet can create. How it can reach across oceans, and how it can bond countries who are completely at war."